CN103095216A - Oscillators and their methods - Google Patents

Abstract

The invention discloses an oscillator and a method thereof, wherein the oscillator comprises a first network, a second network and a cross-coupling network. The first network includes a first amplifier. The first amplifier is arranged in a self-feedback configuration through a first feedback network and is used for generating a first end of an output signal. The second network includes a second amplifier. The second amplifier is arranged in another self-feedback configuration through a second feedback network and is used for generating a second end of an output signal. The cross-coupling network is used for cross-coupling the first end of the output signal and the second end of the output signal. The first network and the second network share a supply current, and the first feedback network and the second feedback network are arranged in a cross-control configuration.

Description

Oscillators and their methods

technical field

The present invention relates to an electronic circuit, in particular to an oscillator and its method.

Background technique

Voltage-controlled oscillators (Voltage-controlled oscillators, VCOs) are widely used in most applications. The voltage-controlled oscillator includes a multi-stage voltage-controlled delay cell (voltage-controlled delay cell; VCDC). Wherein, each stage of voltage-controlled delay unit receives an input from the previous stage and outputs an output to the subsequent stage, and a control voltage controls the circuit delay from the input to the output. FIG. 1 is a schematic diagram of a 3-stage VCO 100 . Referring to FIG. 1 , the voltage-controlled oscillator 100 includes: three voltage-controlled delay units 110 , 120 , 130 , an input, an output, and a circuit delay from the input to the output. Each voltage-controlled delay unit is configured in a balanced (differential) circuit configuration. Each voltage-controlled delay unit has a first (positive) input terminal i ⁺ , a second (negative) input terminal i ⁻ , a first (positive) output terminal o ⁺ , a second (negative) output terminal o ⁻ and a control terminal VC. The input is defined as the voltage difference between the first input terminal i ⁺ and the second input terminal ⁱ⁻ , and the output is defined as the voltage difference between the first output terminal o ⁺ and the second output terminal ^o− . The circuit delay from input to output is controlled by the control voltage VCTL applied to the control terminal VC. The control voltage VCTL is applied to all voltage-controlled delay cells 110-130. The control voltage VCTL determines the circuit delay of the three voltage-controlled delay units 110 - 130 , thus determines the oscillation frequency of the oscillator 100 . The circuit delay of each voltage-controlled delay unit provides a phase shift of the oscillating signal.

To maintain oscillation, the total phase shift must be 360 degrees as this oscillating signal reciprocates around the ring and returns to the starting point. To assist in oscillation, polarity inversion is utilized in this loop to generate a phase shift of 180 degrees, so that the need for a phase shift of circuit delay from this ring to maintain oscillation is reduced to 180 degrees. In the 3-stage VCO 100 of FIG. 1 , polarity inversion is used between the output of the VCO 130 and the input of the VCO 110 . In order to maintain oscillation, each voltage-controlled delay unit must provide a phase offset of 60 degrees. In addition to the need for phase offset, each voltage-controlled delay unit must also provide a gain to the loop to maintain oscillation. There are many circuits suitable for embodying voltage-controlled delay cells. In order to provide this gain, the voltage controlled delay unit must include an amplifier circuit. In order to maintain high-frequency oscillation, the delay of this amplifying circuit must be small, so the amplifying circuit must be a high-speed amplifier. Generally, a high-speed amplifier includes MOS (metal-oxide semiconductor) transistors, resistors and (or) capacitors, and provides a phase shift of no more than 90 degrees. In order to have a phase shift of 180 degrees, at least two stages are required. Therefore, the prior art voltage controlled oscillator includes at least two stages of voltage controlled delay units. In general, single-stage oscillators are only practical when using an inductor to achieve a phase shift of 180 degrees. However, inductors are expensive and unpopular in cost-sensitive designs.

Therefore, how to provide an oscillator without using an inductor is an urgent issue to be solved.

Contents of the invention

The object of the present invention is to provide an oscillator and its method.

In an embodiment, an oscillator of the present invention includes a first network, a second network and a cross-coupling network. The first network includes a first amplifier. The first amplifier is set in a self-feedback topology via a first feedback network, and is used to generate a first end of an output signal. The second network includes a second amplifier. The second amplifier is set in another self-feedback configuration through a second feedback network, and is used to generate a second terminal of an output signal. The cross-coupling network is used for cross-coupling the first end of the output signal and the second end of the output signal.

In one embodiment, an oscillator includes a first self-feedback amplifier, a second self-feedback amplifier and a cross-coupling network. The first self-feedback amplifier is used to output the first end of the output signal, the second self-feedback amplifier is used to output the second end of the output signal, and the cross-coupling network is used to cross-couple the first end of the output signal and the second end of the output signal Two ends. Wherein, the first self-feedback amplifier and the second self-feedback amplifier share a supply current and cross control self-feedback of each other.

In one embodiment, an oscillator includes a first amplifier, a second amplifier, a circuit and a cross-coupling network. The first amplifier includes a first feedback network, and the first feedback network is used to output a first end of an output signal. The second amplifier includes a second feedback network, and the second feedback network is used to output the second terminal of the output signal. The circuit is used to provide a supply current to the first amplifier and the second amplifier, and the cross-coupling network is used to cross-couple the first end of the output signal and the second end of the output signal. Wherein, the first feedback network is controlled by the second terminal of the output signal, and the second feedback network is controlled by the first terminal of the output signal.

In one embodiment, a method of oscillating includes: generating a first end of an output signal by amplifying a first end of an intermediate signal; generating a second end of an output signal by amplifying a second end of an intermediate signal; cross-coupling the output a first end of the signal and a second end of the output signal; coupling the first end of the output signal to the first end of the intermediate signal using a first feedback network controlled by the second end of the output signal; and using the output signal A second feedback network controlled by the first terminal couples the second terminal of the output signal to the second terminal of the intermediate signal.

Description of drawings

FIG. 1 is a schematic diagram of a prior art voltage controlled oscillator.

FIG. 2 is a schematic diagram of an oscillator according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an equivalent circuit of a feedback network of the oscillator of FIG. 2 .

Wherein, the reference signs are explained as follows:

100 VCO

110 voltage controlled delay unit

120 voltage controlled delay unit

130 voltage controlled delay unit

200 oscillators

210 bias current

211 eleventh transistor

212 power supply nodes

220 first amplifier

221 first transistor

222 second transistor

231 third transistor

232 fourth transistor

230 second amplifier

240 First Giving Back Network

241 first resistor

242 second resistor

243 sixth transistor

244 fifth transistor

250 Second Giving Back Network

251 third resistor

252 fourth resistor

253 eighth transistor

254 seventh transistor

260 cross-coupling network

261 ninth transistor

262 tenth transistor

300 Ladder RC Circuit

VCTL control voltage

VC control terminal

i ⁺ first input

i ^- the second input

o ⁺ first output

o ^- the second output

V _DD fixed potential circuit node

I _B supply current

V _CTL control voltage

V _i+ first terminal

V _{i -} the second terminal

V _o+ first terminal

V _o- the second terminal

R1 Front Resistor

R2 rear end resistor

R3 variable resistor

C1 front-end parasitic capacitance

C2 back-end parasitic capacitance

Detailed ways

Hereinafter, a detailed description will be made with reference to the accompanying drawings showing specific embodiments of the present invention. These embodiments are described in sufficient detail to enable those skilled in the art to practice these and other embodiments. When some embodiments are combined with one or more embodiments to form a new embodiment. The various embodiments are not necessarily mutually exclusive. Accordingly, the following detailed description is not intended to be limiting, but rather illustrative.

FIG. 2 is a schematic diagram of an oscillator 200 according to an embodiment of the invention. Referring to FIG. 2 , the oscillator 200 includes: a bias circuit 210 , an amplifier differential pair, a cross-coupling network 260 and a pair of feedback networks. The bias current 210 is used to provide a supply current I _B to the power supply node 212 . The amplifier differential pair includes a first amplifier 220 and a second amplifier 230 and is biased by a supply current I _B from supply node 212 . The amplifier differential pair is used to receive the differential intermediate signal (hereinafter denoted as V _i ) including the first terminal V _i+ and the second terminal V _i- and output the differential signal including the first terminal V _o+ and the second terminal V _o- output signal (labeled V _o hereinafter). Wherein, the first amplifier 220 receives the first terminal V _i+ of the differential intermediate signal V _i and the first terminal V _{o + outputs the differential output signal V o} , and the second amplifier 230 receives the second terminal V of the differential intermediate signal Vi _i- and the second terminal V _o- outputting the differential output signal V _o . The cross-coupling network 260 is used for cross-coupling the first terminal V _o+ of the differential output signal V _o and the second terminal V _o− of the differential output signal V _o . The pair of feedback networks includes a first feedback network 240 and a second feedback network 250 , and the first feedback network 240 and the second feedback network 250 are used to provide feedback to the first amplifier 220 and the second amplifier 230 respectively. Wherein, the first feedback network 240 is controlled by the second terminal V _o− of the differential output signal Vo, and the second feedback network 250 is controlled by the first terminal V _o+ of the differential output signal Vo. The first amplifier 220 is an inverter, and the inverter includes a first transistor 221 and a second transistor 222 . The second amplifier 230 is an inverter, and the inverter includes a third transistor 231 and a fourth transistor 232 . The first feedback network 240 includes a first resistor 241 connected in series, a fifth transistor 244 and a sixth transistor 243 connected in parallel, and a second resistor 242 . Wherein, the fifth transistor 244 and the sixth transistor 243 connected in parallel are configured as variable resistors controlled by the second terminal V _o− of the differential output signal V _o .

The second feedback network 250 includes a third resistor 251 connected in series, a seventh transistor 254 and an eighth transistor 253 connected in parallel, and a fourth resistor 252 . Wherein, the seventh transistor 254 and the eighth transistor 253 connected in parallel are configured as variable resistors controlled by the first terminal V _o+ of the differential output signal V _o . The cross-coupling network 260 includes a ninth transistor 261 and a tenth transistor 262 . The bias circuit 210 includes an eleventh transistor 211 , and the eleventh transistor 211 is used to output the supply current I _B to the power supply node 212 according to the control voltage V _CTL . Here, V _DD represents a fixed potential circuit node. In another embodiment (not shown), the eleventh transistor 211 is removed and the power supply node 212 is directly coupled to the control voltage V _CTL . The principle of the oscillator 200 will be described below.

Anyone skilled in the art should know that there are many types of transistors, and the present invention is not limited to the types of transistors. In one embodiment, the first transistor 221, the third transistor 231, the sixth transistor 243 and the eighth transistor 253 are PMOS transistors, and in one embodiment, the second transistor 222, the fourth transistor 232, the fifth transistor 244, the The seventh transistor 254 , the ninth transistor 261 and the tenth transistor 262 are NMOS transistors.

The first amplifier 220 and the first feedback network 240 form a first half of the oscillator 200 , while the second amplifier 230 and the second feedback network 250 form a second half of the oscillator 200 . Since they share the same supply current I _B , the first half of the oscillator 200 and the second half of the oscillator 200 are of opposite polarity, that is, when the first terminal V _o+ of the differential output signal Vo rises, the differential output signal V The second terminal V _o- of _o falls, and vice versa. For each half of the oscillator 200, the first amplifier 220 and the second amplifier 230 are each 180 degrees out of phase due to the inverting nature of the amplifiers, and due to the parasitic capacitive loading at the outputs of the amplifiers. load) resulting in an additional 90-degree phase shift. Note that each MOS transistor results in a parasitic capacitance. Although the first amplifier 220 and the second amplifier 230 respectively have a limited output resistance, the limited output resistance can be canceled by the cross-coupling network 260 . Here, the limited output resistance reduces the additional phase shift to less than 90 degrees. The cross-coupling network 260 in the differential circuit configuration is equivalent to a negative resistor that cancels the finite output resistance.

For each half of the oscillator 200 , the first feedback network 240 and the second feedback network 250 are respectively equivalent to a ladder RC circuit 300 , as shown in FIG. 3 . The ladder RC circuit 300 includes a front-end resistor R1 (representing the first resistor 241 or the third resistor 251), a front-end parasitic capacitance C1 (of the sixth transistor 243 and the fifth transistor 244, or of the eighth transistor 253 and the seventh transistor 254 ), variable resistor R3 (representing the resistance value of the sixth transistor 243 connected in parallel with the fifth transistor 244, or the resistance value of the eighth transistor 253 connected in parallel with the seventh transistor 254), the back-end parasitic capacitance C2 (which is the sixth transistor 243 and the fifth transistor 243 transistor 244 , or the eighth transistor 253 and the seventh transistor 254 ), and the back-end resistor R2 (representing the first resistor 241 or the third resistor 251 ). As such, the ladder RC circuit 300 suffices to provide a phase shift of 90 degrees. Therefore, a total phase shift of 360 degrees is achieved to sustain the oscillation through the use of amplifiers (ie, first amplifier 220 and second amplifier 230 ) and feedback networks (ie, first feedback network 240 and second feedback network 250 ). The two halves of this oscillator are controlled alternately, that is, the first feedback network 240 of the first half is controlled by the output of the second half (ie, the second terminal V _o- ), while the second feedback network 240 of the second half The network 250 is controlled by the output of the first half (ie, the first terminal V _o+ ). When the amplitude of the output signal is large, such a configuration architecture improves the strength of the feedback by reducing the total effective resistance of the feedback network (ie, the first feedback network 240 and the second feedback network 250), thus helping to achieve a higher Oscillation frequency.

Although the technical content of the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention, and any changes and modifications made by those skilled in the art without departing from the spirit of the present invention shall be covered by this disclosure. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent claims.

Claims (20)

1. oscillator comprises:

One first network comprises one first amplifier, is arranged in a self feed back configuration via one first feedback network, to produce the first end of an output signal;

One second network comprises one second amplifier, is arranged in another self feed back configuration via one second feedback network, to produce the second end of this output signal; And

One cross-couplings network, in order to this first end of this output signal of cross-coupled and this second end of this output signal, wherein this first feedback network and this second feedback network are arranged on one across in the control configuration.

2. oscillator as claimed in claim 1, wherein this first feedback network comprises one first resistance and a first transistor of series connection, this the first transistor is to be controlled by this second end of this output signal, and this second feedback network comprises one second resistance and a transistor seconds of series connection, and this transistor seconds is to be controlled by this first end of this output signal.

3. oscillator as claimed in claim 2, wherein when the amplitude of this second end of this output signal increases, the total resistance of this first feedback network reduces, and when the amplitude of this first end of this output signal increases, total amplitude reduction of this second feedback network.

4. oscillator as claimed in claim 3, wherein this first feedback network more comprises one the 3rd resistance, and the 3rd resistance is connected with this first transistor, and this second feedback network more comprises one the 4th resistance, and the 4th resistance is connected with this transistor seconds.

5. oscillator as claimed in claim 1, wherein this first network and this second network share one for induced current.

6. oscillator as claimed in claim 5 more comprises: power supply circuits provide this confession induced current in order to control voltage according to one.

7. oscillator as claimed in claim 1, wherein this cross-couplings network is to arrange that to be used as this first amplifier and this second amplifier be the load with negative resistance value.

8. oscillator comprises:

One first amplifier comprises one first feedback network, in order to export the first end of an output signal;

One second amplifier comprises one second feedback network, in order to export the second end of this output signal;

One circuit supplies induced current to this first amplifier and this second amplifier in order to provide one; And

One cross-couplings network, in order to this first end of this output signal of cross-coupled and this second end of this output signal, wherein this first feedback network is to be controlled by this second end of this output signal, and this second feedback network is to be controlled by this first end of this output signal.

9. oscillator as claimed in claim 8, wherein this first feedback network comprises one first resistance and a first transistor of series connection, this the first transistor is to be controlled by this second end of this output signal, and this second feedback network comprises one second resistance and a transistor seconds of series connection, and this transistor seconds is to be controlled by this first end of this output signal.

10. oscillator as claimed in claim 9, wherein when the amplitude of this second end of this output signal increases, the total resistance of this first feedback network reduces, and when the amplitude of this first end of this output signal increases, total amplitude reduction of this second feedback network.

11. oscillator as claimed in claim 10, wherein this first feedback network more comprises one the 3rd resistance, and the 3rd resistance is connected with this first transistor, and this second feedback network more comprises one the 4th resistance, and the 4th resistance is connected with this transistor seconds.

12. oscillator as claimed in claim 8, wherein this confession induced current is to control voltage by one to be controlled.

13. oscillator as claimed in claim 8, wherein this cross-couplings network is to arrange that to be used as this first amplifier and this second amplifier be the load with negative resistance value.

14. oscillator as claimed in claim 8, wherein this first feedback network and this second feedback network arrange respectively to produce 90 degree phase deviations of this second end of this first end of this output signal and this output signal.

15. an oscillation method comprises:

Produce the first end of an output signal by the first end that amplifies a M signal;

Produce the second end of this output signal by the second end that amplifies this M signal;

This second end of this first end of this output signal of cross-coupled and this output signal;

One first feedback network that use is controlled with this second end of this output signal is coupled to this first end of this output signal this first end of this M signal; And

One second feedback network that use is controlled with this first end of this output signal is coupled to this second end of this output signal at this second end of this M signal.

16. oscillation method as claimed in claim 15, wherein this first feedback network comprises one first resistance and a first transistor of series connection, this the first transistor is to be controlled by this second end of this output signal, and this second feedback network comprises one second resistance and a transistor seconds of series connection, and this transistor seconds is to be controlled by this first end of this output signal.

17. oscillation method as claimed in claim 16, wherein when the amplitude of this second end of this output signal increases, the total resistance of this first feedback network reduces, and when the amplitude of this first end of this output signal increases, total amplitude reduction of this second feedback network.

18. oscillation method as claimed in claim 17, wherein this first feedback network more comprises one the 3rd resistance, and the 3rd resistance is connected with this first transistor, and this second feedback network more comprises one the 4th resistance, and the 4th resistance is connected with this transistor seconds.

19. oscillation method as claimed in claim 15 is wherein controlled voltage control one confession induced current according to one, and this first feedback network and shared this confession induced current of this second feedback network.

20. oscillation method as claimed in claim 15, wherein this first feedback network and this second feedback network arrange respectively to produce 90 degree phase deviations of this second end of this first end of this output signal and this output signal.

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